Lead-Free Inorganic Cesium Tin-Germanium Triiodide Perovskites for Photovoltaic Application

The toxicity of lead associated with the lifecycle of perovskite solar cells (PSCs( is a serious concern which may prove to be a major hurdle in the path toward their commercialization. The current proposed lead-free PSCs including Ag(I), Bi(III), Sb(III), Ti(IV), Ge(II), and Sn(II) low-toxicity cations are still plagued with the critical issues of poor stability and low efficiency. This is mainly because of their chemical stability. In the present research, utilization of all inorganic CsSnGeI₃ based materials offers the advantages to enhance resistance of device to degradation, reduce the cost of cells, and minimize the carrier recombination. The presence of inorganic halide perovskite improves the photovoltaic parameters of PCSs via improved surface coverage and stability. The inverted structure of simulated devices using a 1D simulator like solar cell capacitance simulator (SCAPS) version 3308 involves TCOHTL/Perovskite/ETL/Au contact layer. PEDOT:PSS, PCBM, and CsSnGeI₃ used as hole transporting layer (HTL), electron transporting layer (ETL), and perovskite absorber layer in the inverted structure for the first time. The holes are injected from highly stable and air tolerant Sn_0.5Ge_0.5I₃ perovskite composition to HTM and electrons from the perovskite to ETL. Simulation results revealed a great dependence of power conversion efficiency (PCE) on the thickness and defect density of perovskite layer. Here the effect of an increase in operating temperature from 300 K to 400 K on the performance of CsSnGeI₃ based perovskite devices is investigated. Comparison between simulated CsSnGeI₃ based PCSs and similar real testified devices with spiro-OMeTAD as HTL showed that the extraction of carriers at the interfaces of perovskite absorber depends on the energy level mismatches between perovskite and HTL/ETL. We believe that optimization results reported here represent a critical avenue for fabricating the stable, low-cost, efficient, and eco-friendly all-inorganic Cs-Sn-Ge based lead-free perovskite devices.

• Seyedeh Mozhgan Seyed-Talebi
• Javad Beheshtian

• Hole transporting layer
• lead-free
• perovskite Solar cell
• SCAPS-1D
• Sn-Ge based material.

[1] S. Nair, S. B. Patel, and J. V. Gohel, “Recent trends in efficiency-stability improvement in perovskite solar cells”, Mater. Today Energy, 2020, 17, 100449.
[2] Y. Zhou, and Y. Zhao, “Chemical stability and instability of inorganic halide perovskites,” Energy Environ. Sci., 2019, 12, pp. 1495-1511.
[3] S. Shao, J. Liu, G. Portale, H. ‐H. Fang, G. R. Blake, G. H. Brink, L. J. Anton Koster, and M. A. Loi, “Highly reproducible Sn-based hybrid perovskite solar cells with 9% efficiency”, Adv. Energy Mater., 2018, 8, 1702019.
[4] L. Peng, and W. Xie, Theoretical and experimental investigations on the bulk photovoltaic effect in lead-free perovskites MASnI3 and FASnI3, RSC Adv., 2020, 10, pp. 14679-14688.
[5] B. Kima, and S. I. Seok, “Molecular aspects of organic cations affecting the humidity stability of perovskites,” Energy Environ. Sci., 2020, 13, pp. 805-820.
[6] T. Handa, T. Yamada, H. Kubota, S. Ise, Y. Miyamoto, Y. Kanemitsu, “Photocarrier recombination and injection dynamics in long-term stable lead-free CH3NH3SnI3 perovskite thin films and solar cells, ” J. Phys. Chem. C., 2017, 121, pp. 16158–16165.
[7] T. Bin Song, T. Yokoyama, S. Aramaki and M. G. Kanatzidis, “Performance Enhancement of Lead-Free Tin-Based Perovskite Solar Cells with Reducing Atmosphere-Assisted Dispersible Additive,” ACS Energy Lett, 2017, 2 (4), pp. 897-903.
[8] T. Zhang, H. Li, H. Ban, Q. Sun, Y. Shen, and M. Wang, “Efficient CsSnI3-based inorganic perovskite solar cells based on mesoscopic metal oxide framework via incorporating donor element,” J. Mater. Chem. A, 2020, 8 (7), pp. 4118-4124.
[9] N. Wang, Y. Zhou, M. G. Ju, H. F. Garces, T. Ding, S. Pang, X. C. Zeng, N. P. Padture, and X. W. Sun, “Heterojunction‐Depleted Lead‐Free Perovskite Solar Cells with Coarse‐Grained B‐γ‐CsSnI3 Thin Films,” Adv. Energy Mater. 2016, 6(24), 1601130.
[10] G. E. Eperon, G. M. Paternò, R. J. Sutton, A. Zampetti, A. A. Haghighirad, F. Cacialli, and H. J. Snaith, “Inorganic Cesium Lead Iodide Perovskite Solar Cells, ” J. Mater. Chem. A, 2015, 3, pp. 19688-19695.
[11] P. Luo, W. Xia, S. Zhou, L. Sun, J. Cheng, C. Xu, and Y. Lu, “Solvent Engineering for an Ambient-Air-Processed, Phase-Stable CsPbI3 in Perovskite Solar Cells,” J. Phys. Chem. Lett. 2016, 7 (18), pp. 3603-3608.
[12] M. Chen, M. -G. Ju, H. F. Garces, A. D. Carl, L. K. Ono, Z. Hawash, Y. Zhang, T. Shen, Y. Qi, R. L. Grimm, D. Pacifici, X. C. Zeng, Y. Zhou, and N. P. Padture, “Highly stable and efficient all-inorganic lead-free perovskite solar cells with native-oxide passivation,” Nature Communications, 2019, 10, 16.
[13] M. Burgelman, P. Nollet, S. Degrave, “Modeling polycrystalline semiconductor solar cells,” Thin Solid Films, 2000, 527, pp. 361–362.
[14] S. Shao, and M. A. Loi, “The Role of the Interfaces in Perovskite Solar Cells, ADV. Mater. Interfaces,” 2020, 7(1), 1901469.
[15] S. Wang, T. Sakurai, W. Wen, Y. Qi, “Energy Level Alignment at Interfaces in Metal Halide Perovskite Solar Cells,” Adv. Mater. Interfaces, 2018, 5(22):1800260.
[16] A. Al Mamun, T. T. Ava, K. Zhang, H. Baumgart, and G. Namkoong, “New PCBM/carbon based electron transport layer for perovskite solar cells, ” Phys. Chem. Chem. Phys., 2017, 19, 17960.
[17] M. B. Faheem, B. Khan, C. Feng, M. U. Farooq, F. Raziq, Y. Xiao, and Y. Li, “All-Inorganic Perovskite Solar Cells: Energetics, Key Challenges, and Strategies toward Commercialization,” ACS Energy Lett. 2020, 5, pp. 290−320.